If anyone is interested, i was trying to figure out how to map a route and have the GPS follow that exact route. it could be handy if you wanted to say take the scenic route for example.
i used bing maps. start out by adding a push pin at the start point, then draw out your map with the highlighter tool. now keep in mind, that every time you click a point to change the direction of the highlighted route, the GPS in the car sees that as a destination, so try to go easy on them. when you're finished, you can save the route as a .KLM file.
put it onto a USB stick, plug it into the car, and the route will pop up on the GPS, name the end point "end", and set that as your destination, then you can go into the menu on the GPS and add in destinations along the way from the memory stick. the gps will guide you to each click that you made on the route.